The subject disclosure relates generally to axle/suspension systems for heavy-duty vehicles. In particular, the subject disclosure relates to an axle/suspension system with structure that limits pivotal movement of a beam and axle of the axle/suspension system.
Beam-type axle/suspension systems have been used in heavy-duty vehicles for many years. Beam-type axle/suspension systems typically include a pair of suspension assemblies. In some heavy-duty vehicles, the suspension assemblies are connected to a frame or subframe of the vehicle. Reference is made generally to a heavy-duty vehicle for the purpose of convenience with the understanding that such reference includes trucks, tractor-trailers and semi-trailers, trailers, and the like. Reference is made generally to a frame for the purpose of convenience with the understanding that such reference is by way of example and includes main or primary frames, movable subframes or sliders, nonmovable subframes, and the like.
A pair of laterally-spaced hangers is attached to and depends from the frame of the heavy-duty vehicle. The suspension assembly includes a pair of longitudinally-extending elongated beams. Each beam is pivotally mounted at one of its end portions to a respective hanger. An axle extends transversely between, and typically is attached to, the beams at an end or intermediate portion of the beam located opposite the pivotal connection end. The beam end portion opposite the pivotal connection end is also typically connected to an air spring, which is connected to the frame. The axle/suspension system may include a ride-height control valve mounted on the frame or other support structure to adjust the ride-height of the heavy-duty vehicle. Ride-height is defined as a static distance from the bottom of a frame member to a longitudinal central axis of the axle. The ride-height control valve is operatively connectable with the beam and the air spring in order to maintain a desired ride-height of the heavy-duty vehicle. A brake system of the heavy-duty vehicle may be mounted on the axle/suspension system, along with one or more shock absorbers that provide damping to the axle/suspension system, typically if a non-damping air spring is employed.
The axle/suspension system of the heavy-duty vehicle acts to provide ride, handling, and damping characteristics. For example, as the heavy-duty vehicle is traveling over the road, its tires and wheels encounter road conditions that impart various forces, loads, and/or stresses, collectively referred to as forces, to the respective axle on which the tires and wheels are mounted. In turn, the forces are transferred to the suspension assemblies that connect with and support the axle. In order to minimize the detrimental effect of these forces on the heavy-duty vehicle as it is operating, the axle/suspension system is designed to react and/or absorb at least some of the forces.
These forces include vertical forces caused by vertical movement of the tires and wheels as they encounter certain road conditions, fore-aft forces caused by acceleration and deceleration of the vehicle, and lateral and torsional forces associated with transverse vehicle movement, such as turning of the vehicle and lane-change maneuvers. In order to address the application of such different forces, axle/suspension systems have differing structural and operational requirements. The axle/suspension system often needs to be fairly stiff to minimize the amount of sway experienced by, and provide roll stability to, the heavy-duty vehicle. The axle/suspension system also often needs to be relatively flexible to assist in cushioning the vehicle from vertical forces. This provides compliance, allowing the components of the axle/suspension system to withstand the forces and allowing damping of the vibrations or oscillations resulting from such forces. As a result, the axle/suspension system often requires critical components, such as air springs and/or shock absorbers, to cushion the ride of the vehicle from vertical impacts and provide damping characteristics.
Air springs of the type utilized in heavy-duty axle/suspension systems typically include a flexible bellows mounted to the frame and operatively connected to a piston mounted to the beam. Shock absorbers of the type utilized in heavy-duty axle/suspension systems are typically mounted on and extend between the elongated beam and the hanger or the frame of the heavy-duty vehicle and include a cylinder and a piston rod reciprocating within the cylinder. Both air springs and shock absorbers have structural limitations, which limit their ability to extend with downward pivotal movement of the axle.
During operation, the heavy-duty vehicle may strike a pothole or may be lifted onto a railroad car, resulting in the beam of the suspension assembly pivoting or rotating downwardly about the hanger. Similarly, when the heavy-duty vehicle, such as a trailer, is reversing, the trailer brakes may be actuated, referred to as reverse braking, causing the suspension assembly to extend downwardly. In such situations, the air spring and/or shock absorber greatly extend or stretch between the beam and the frame. Both the air spring and shock absorber may be capable of limited extension. Thus, the air spring and/or shock absorber provides some restriction on the relative pivotal movement of the beam of the axle/suspension system. However, the air spring and shock absorber can be damaged if the tensile load produced by the extension exceeds the structural limitations of the air spring and/or shock absorber. As a result, the air spring, shock absorber, and/or other critical components of the axle/suspension system may be damaged. Thus, it is desirable for the axle/suspension system to minimize damage to such critical components. Specifically, it is desirable to limit pivotal movement of the beam about the hanger to prevent over-extension of the air spring and/or shock absorber.
In some heavy-duty vehicles, devices that operate in tension, such as chains, straps, cables, wire ropes, or the like, have been used to minimize the possible damage to the air spring and/or shock absorber as a result of over-extension. These devices are generally disposed between the hanger or frame of the heavy-duty vehicle and the beam of the suspension assembly to act as positive mechanical limiting structures, or down stops. The devices limit the pivotal movement of the beam of the suspension assembly, reducing the extension or stretching that the air spring and/or shock absorber may experience. These devices minimize the possibility of potential damage to the air spring, shock absorber, and/or other components of the axle/suspension system. Because these devices are disposed beneath the heavy-duty vehicle, they may be exposed to road splash and debris that could damage the devices. The devices are often manufactured to be relatively robust in order to withstand the weight of and forces acting on the axle/suspension system. This results in the devices increasing the weight and cost of operating the heavy-duty vehicle while decreasing available space in the already limited undercarriage of the heavy-duty vehicle and axle/suspension system.
Thus, a need exists for an axle/suspension system for a heavy-duty vehicle that provides a positive mechanical down stop that is simple, durable, light weight, and compact and that limits pivotal movement of the beam to avoid potential damage to the air spring, shock absorber, and/or other components of the axle/suspension system during operation of the vehicle.